Those pictures of Lara's ass isn't herpes or genital warts or even syphilis... go to google.com and check out all the images of those STD's it's nothing like whats on her butt.
Although before these pictures were taken she did a double anal scene(?) with Darren James and whomever the other guy is, right? Well she had never done that before.
It looks like she apparently just shaved shortly before the shoot. Long period of constant friction around that area, where there's heat and moisture on top of it all with open pores can cause an irritation like that. Pimple-like rash.
It's all on her lower butt area, not her genitals. Warts grow distinctively on the genital area, herpies usually show up in the same vicinity as well as syph.
Although, I wouldn't doubt she's the one that caused the HIV situation.
I think the lab should look at the levels of antibodies in both Darren and Lara and compare the two. Sometimes you can distinguish who's been infected longest. By the age of antibodies blahb lah blah you get the picture.